1. Field of the Invention
The present invention relates to an exhaust control valve, and more particularly to an exhaust control valve controlling the flow of exhaust gas from an internal combustion engine of a vehicle.
2. Background Art
An exhaust valve in which a bearing bushing for rotatably bearing a valve shaft and a seal member adjacent to the bearing bushing and making close contact with an external circumferential surface of the valve shaft are mounted in a valve housing has been taught by the background art. Japanese Pre-examination Patent Publication (KOKAI) No. 63-212728 (1988) shows an exemplary arrangement of this type of exhaust control valve.
However, these types of exhaust control valve suffer from the following disadvantages. Since a bearing bushing and a seal member are both utilized, the number of component parts is increased. In addition, each of the bearing bushing and the seal member(s) provided exclusive functions. Finally, the seal member(s) are expensive, and therefore making it difficult to reduce construction costs.
The present invention overcomes the shortcomings associated with the conventional art and achieves other advantages not realized by conventional art.
An aspect of the present invention is to provide an exhaust control valve reducing the number of component parts.
An additional aspect of the present invention is to providing an inexpensive bearing bushing that provides a sealing function in an exhaust control valve.
These and other aspects of the present invention are accomplished by an exhaust control valve for an internal combustion engine for a vehicle comprising a valve housing having a valve chamber; a valve body rotatably contained in the valve chamber and cooperatively engaged with the valve housing for controlling a flow of exhaust gas;
a rotating transmission member drivingly engaging at least one valve shaft of the valve body, the transmission member secured to an outer end of the at least one valve shaft protruding from an exterior of the valve housing; a bearing bushing for rotatably bearing an external circumferential surface of the valve shaft by an internal circumferential surface of the bearing bushing, the bearing bushing rotatably bearing an end face of the valve body; and a spring operatively engaged with the valve body and maintaining a pressure contact seal condition between a pair of opposed end faces of the bearing bushing and the valve body.
According to a first feature of the present invention, a bearing bushing can be provided that offers a bearing function and a sealing function. Therefore, leakage of exhaust gas from the vicinity of a valve shaft can be prevented without providing a special seal member. Further, a reduction in cost can be achieved as expensive seal members are eliminated and the number of component parts is reduced.
In addition, since seal members are not used, it is possible to use a bearing bushing that is relatively long in its axial direction. Accordingly, a bearing shaft can be supported with a larger supporting surface/region, thereby ensuring a large bearing capacity. Therefore, the bearing bush can display superior durability even though it receives load directly from a driven pulley fitted to the valve shaft.
According to a second feature of the present invention, the nonmetallic bearing bushing displays a good sealing function and absorbs vibrations in the thrust direction of the valve body arising from exhaust pulsations. Accordingly, the generation of abnormal noise is further suppressed.
Furthermore, the invention has a third feature whereby the valve body is formed from a titanium material together with its valve shafts, while the bearing bushes are formed from a carbon material.
According to this third feature, the valve body is formed from a titanium material together with its valve shafts, whereby it is therefore possible to achieve a reduction in the weight of the valve body and, hence, the exhaust control valve. Although the titanium material of the valve body as a whole is an active metal, and has a high tendency toward seizure, the adoption of the bearing bushing formed from a carbon material makes it possible to give achieve rotational slidability between the valve shafts and the bearing bushings even in high-temperature conditions. This, in cooperation with the reduction of weight of the valve body, makes it possible to effectively enhance the response property of the valve body to driving torque.
These and other aspects of the present invention are further accomplished by An exhaust control system for an internal combustion engine of a vehicle comprising a plurality of exhaust pipes each having an intermediate portion; an exhaust gas muffler operatively connected to the exhaust pipes; a valve housing disposed in the intermediate portion of the exhaust pipes and having a valve chamber; a valve body rotatably contained in the valve chamber and cooperatively engaged with the valve housing for controlling a flow of exhaust gas; a rotating transmission member drivingly engaging at least one valve shaft of the valve body, the transmission member secured to an outer end of the at least one valve shaft protruding from an exterior of the valve housing; a bearing bushing for rotatably bearing an external circumferential surface of the valve shaft by an internal circumferential surface of the bearing bushing, the bearing bushing rotatably bearing an end face of the valve body; and a thrust spring operatively engaged with the valve body and maintaining a pressure contact seal condition between a pair of opposed end faces of the bearing bushing and the valve body.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.